Digital camera for recording a still image while shooting a moving image

ABSTRACT

In a digital camera, when snapshot shooting is instructed during recording of a moving image, a shot still image is temporarily pushed aside in a memory area for use in pushing aside ( 7   a ) in a frame buffer ( 7 ). A currently shooting motion image and a still image are displayed in parallel on a display ( 9 ), so that a user can confirm a content of a snapshot. The moving image continues to be recorded even during a push-aside operation. After a moving image processing is completed, the still image is processed by an image correcting circuit ( 4 ). The frame buffer ( 7 ) comprises a plurality of frame recording areas, and is shared on the occasions of a moving image processing and a still image processing. In a normal moving image processing, these areas are utilized in a cyclic manner, and when the still image is shot, any of areas will be utilized. Thereafter, the rest of areas are utilized in the cyclic manner for the moving images. The recording function for the moving image and still image is improved at low cost, it becomes easy to take a snapshot, and the merchandise size is not increased.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 10/148,886,filed on Oct. 18, 2002, and wherein application Ser. No. 10/148,886 is anational stage application filed under 35 USC §371 of InternationalApplication No. PCT/JP00/08977, filed Dec. 18, 2000, the contents ofwhich are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a digital camera such as a memorycontrol device and an electronic still camera. The present inventionalso relates to an image processing method and an image processingapparatus which can be used therefor. The present invention relates totechnology in which to code or decode according to the MPEG (MovingPicture Expert Group) and JPEG (Joint Photographic Coding Expert Group)standards, and relates to apparatuses which utilize the technology.

BACKGROUND TECHNOLOGY

In recent years, the demand for electronic still cameras is expanding inthe place of cameras using the silver-salt photographing technologydeveloped since 19th century. In the electronic still camera, “JPEG” isused as a data compression and expansion technique in order toefficiently process image data on the occasions of transmitting andstoring the image data. A technical core of the JPEG method lies in thediscrete cosine transform (DCT).

Since the compression and expansion of moving image data are alsopossible according to the JPEG method, there is an electronic stillcamera using this method, which is equipped with a shooting function ofthe moving image. The technology in which the moving image data arecompressed and expanded in units of frame by the JPEG method is calledM-JPEG (Motion-JPEG).

On the other hand, “MPEG” is one of techniques in which to compress andexpand multimedia data including moving images. In the MPEG method, thetechnical core used in the video part lies in motion compensatedprediction (MC) and DCT. The coding technique combining MC and DCT iscalled the hybrid coding technique. It can be said that the MPEG methodis the technique in which the MC is combined into the JPEG method.

In the electronic still camera utilizing the MPEG method, it is desiredthat a snapshot which corresponds to one frame of the moving image canbe recorded during the shooting of the moving image; for example, such atechnique is disclosed in Japanese Patent Application Laid-Open No.Hei11-75148. It is known that in this type of electronic still camerathere is provided an exclusive-use memory area for use in pushing asideand storing snapshot data. However, in this type of camera, thisexclusive-use memory area is not utilized until the snapshot shooting isinstructed, so that the effective usage rate of the memory during theshooting of moving image is not enhanced. Making it compact-size andlow-cost plays a crucial role in evaluation of merchandise values, andit is admitted that there is a room for improvement in terms ofimplementing area and cost performance. This is the first problem whichthe inventor of the present invention recognized.

The second problem which the inventor recognized relates also to thesimilar room for improvement. Since the photographed snapshot isoftentimes printed on paper medium by using a video printer or the like,high image quality is required. However, when the moving image isrecorded with the same high image quality as the snapshot, the memorycapacity runs out quickly. Thus, a technique is known in which the stillimage is recorded at the same pixel density level as that in theshooting of the still image, and the moving image whose pixel density isreduced after performing a filtering processing thereon is recorded. Inthis conventional technique, however, the edge smoothing of the stillimage or emphasis processing thereof, for example, and so forth can notbe performed, thus a filter circuit needs to be newly provided in orderto realize these functions.

The third problem that the inventor recognized relates to the usabilityof a user at the time of shooting a snapshot. Conventionally, theoutcome of the photographed snapshot is confirmed only after theshooting of the moving image is completed, so that there are manyoccasions where the proper photographing of the snapshot is missed outwhen the shooting of the snapshot is mistaken. Moreover, provision oftwo shooting modes for the moving image and snapshot is not likely tobecome a use-friendly design.

DISCLOSURE OF THE INVENTION

Therefore, an objective of the present invention is to provide atechnique in which to give merits in terms of implementing area or costperformance thereof in the digital cameras and related technical fieldthereof. Another objective of the present invention is to provide atechnique in which to realize further user-friendly merchandise in thedigital cameras and the related technical field. These objectives andthose related thereto become gradually clearer hereinafter.

A certain mode of the present invention relates to an image processingapparatus. This apparatus comprises: a signal processing circuit which,after performing at least gamma correction or white balance adjustmenton image data, outputs the image data, a still image encoder which codesthe image data as a still image; a moving image encoder which codes theimage data as a series of motion images; an image correcting unit,provided in an input route of the image data leading to the still imageencoder and the moving image encoder, which performs a filteringprocessing on the image data; and a control unit which controls a seriesof these processings.

By implementing this structure, both the still image and the motionimage can be filtering-processed by the same image correcting unit.Those filtering processings may be set in a manner such that contentsthereof are made different. For example, the filtering processingperformed on the image data for the still image encoder (hereinafterreferred to as a “first filtering processing” also) may include a pixelvalue transform processing, and the filtering processing performed onthe image data for the moving image encoder (hereinafter referred to asa “second filtering processing” also) may include a pixel densitytransform processing. A plurality of types of the first filteringprocessings may be prepared and there may be provided a selector whichselects a desirable filtering function from these processings. Thefiltering processing may be able to be set to an identity transformprocessing in which an input coincides with an output.

This apparatus may further comprise a storage unit which temporarilystores image data for one frame, in response to a still image recordinstructing signal during a coding processing by the moving imageencoder. This image data may be image data prior to or after correctionby the image correcting unit.

Another mode of the present invention relates to an image processingmethod. In this method, a filtering processing is performed on imagedata, both generated through at least gamma correction or white balanceadjustment, to be coded as a still image (hereinafter possiblyabbreviated simply as “still image data”) and image data to be coded asa moving image (hereinafter possibly abbreviated simply as “moving imagedata”), by a common image correcting unit. According to this method, anedge emphasis processing, for example, can be performed on the stillimage data, and a pixel number reduction processing can be performed onthe motion image data.

Still another mode of the present invention relates an image processingmethod. In this method, a processing route of the still image data andthat of the moving image data, both data having been processed by asignal processing circuit, are unified, so that they are inputted to acommon image correcting unit; and a predetermined processing isperformed in a time sharing manner. Namely, at the timing of performingrespective processings on the still image data and the moving imagedata, the image correcting unit operates as the same or differentprocessor. When the image correcting unit performs the filteringprocessings and the still image data and moving image data areprocessed, a filter coefficient may be dynamically changed.

Still another mode of the present invention relates to a digital camera.This camera includes: a signal processing circuit which performs aprocessing, including an A-D conversion, on a shot image signal; a stillimage encoder which codes image data outputted from the signalprocessing circuit, as a still image; a moving image encoder which codesthe image data as a series of moving images; and an image correctingunit, provided in an input route of the image data leading to the stillimage encoder and the moving image encoder, which performs a filteringprocessing on the image data.

Still another mode of the present invention relates to a digital camera.This camera is capable of recording a still image during shooting of amoving image, and it comprises: a display control unit which generatesan image signal by which shot image data are displayed on a display; anda control unit which, while the shot image data are being displayed onthe display as a moving image, instructs the display control unit todisplay on the display a still image corresponding to part of the movingimage, for example the still image corresponding to one frame. By thisstructure, when a snapshot is photographed during the recording of themoving image, the contents thereof can be confirmed, so that if theoutcome thereof is not satisfactory one can shoot again anothersnapshot.

Still another mode of the present invention relates to a digital camera.This camera comprises: a still image encoder which codes shot image dataas a still image; a moving image encoder which codes the shot image dataas a series of moving images; a recording unit which records image datacoded by the still image encoder and the moving image encoder; a displaycontrol unit which generates an image signal by which the shot imagedata are displayed on a display; and a control unit which controls aseries of processings, wherein the control unit is structured such that,while the shot image data are being displayed on the display as a movingimage, image data shot at a timing responsive to a still image shootinginstruction signal is displayed on the display. This camera may furthercomprise a unit, such as an operational button and a switch or the like,which inputs a shooting instruction of the still image.

The control unit may control the display control unit in a manner suchthat the motion image and the still image are displayed in parallel. Byoperations of the control unit, either one of the still image or themotion image displayed in parallel may be set to a main picture of thedisplay so as to be displayed thereon, and these may be switchable, and,for example, permission or denial of the display of the still image maybe able to be set. The still image may be displayed for a predeterminedperiod of time, and the displayed period of time may be determinedaccording to a user's instruction. When the still image is displayed,the user may be able to erase it, for example, by pressing apredetermined button.

Still another mode of the present invention relates to a digital camera.This camera is capable of recording a snapshot during shooting of themoving image, and it comprises: a display control unit which generatesan image signal by which shot image data are displayed on a display; anda control unit which, while the shot image data are being displayed onthe display as a moving image, instructs the display control unit todisplay the snapshot on the display.

Still another mode of the present invention relates to an imageprocessing method in the digital camera. This method includes: aprocessing of shooting a moving image; a processing of shooting asnapshot during shooting of the moving image; a processing of displayingthe shot moving image; and a processing of displaying the shot snapshot,wherein the moving image and the snapshot are displayed in the digitalcamera in a simultaneously visible manner. In addition to a case inwhich the motion image and the snapshot are displayed in parallel on asingle display, they may be displayed on different displays and itsuffices as long as they are simultaneously visible. Moreover, thissimultaneous visible state may be generated for a predetermined limitedduration of time.

Still another mode of the present invention relates to a memory controldevice. This device comprises: a storage unit which includes a pluralityof memory areas which sequentially stores inputted data; and a controlunit which controls input-output of the storage unit in a manner thatthe memory areas are used cyclically, wherein input-output of thestorage unit is controlled by the control unit in a manner that, whenthe control unit stores data in arbitrary memory area within a pluralityof the memory areas, the remaining memory areas are used cyclically. Ineach memory area, the data may be stored in predetermined units ofblock, for example in units of image frame or in units of data's codedgroup.

Still another mode of the present invention relates to a digital camera.This digital camera is equipped with the above-described memory controldevice and is capable of recording a still image corresponding to partof a moving image during shooting of the moving image. The storage unitsequentially stores inputted moving image data in a plurality of thememory areas. The control unit controls input-output of the storage unitin a manner that when the data are taken in at a store-the-still-imageinstructing timing, in a plurality of the memory areas the moving imagedata are taken into the remaining memory areas excluding the memory areawhich stored said data.

The control unit may control in a manner that when data are again takenin at the store-the-still-image instructing timing, previously storeddata are cancelled, namely, overwrite by other data is permitted, andthe moving image data are taken into the rest of the memory areasexcluding the memory area which stores newly taken-in data.Alternatively, it may control in a manner that the moving image data aretaken into the remaining memory areas excluding the memory areas thatstore the previously stored data and the memory areas that store newlytaken-in data.

Still another mode of the present invention relates to an imageprocessing apparatus equipped with a memory control device whichperforms a control by which image data are stored in a memory. Thismemory includes a put-to-common-use area which temporary stores movingimage data and still image data so as to be respectively given topredetermined image processings. When storing the still image data, thememory control device utilizes an area, in the put-to-common-use area,having moving image data whose processing has been completed, and whenstoring the moving image data the memory control device sequentiallyutilizes areas other than those which store unprocessed still image datain the put-to-common-use area.

A digital camera equipped with this image processing apparatus may beprovided. In that case, when shooting of a still image is instructed forthe second time during shooting of a moving image, the memory controldevice, on the occasion of storing still image data for the second time,may utilize an area other than that which stores the still image datashot for the first time. This digital camera may further comprise acontrol unit which, according to a user's instruction, selects eitherone of the still image data shot for the first time or the still imagedata shot for the second time, so as to be finally stored. Moreover, onthe occasion of storing still image data for the second time, the areawhich stores the still image data shot for the first time, may beutilized by overwriting contents thereof.

Moreover, arbitrary combinations of the above-described elements and soforth, as well as expressions thereof changed between a method, anapparatus, a recording medium, a computer program, etc. are encompassedby the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above described objectives, other objectives, features andadvantages are further made clear by the following preferred embodimentsand drawings accompanied thereby.

FIG. 1 is a block circuit diagram showing an electronic still cameraaccording to an embodiment in which the present invention is embodied.

FIG. 2 is a schematic block diagram showing a JPEG core circuit and anMPEG core circuit according to the present embodiment.

FIG. 3 is a schematic block diagram showing an image data correctingcircuit according to the present embodiment.

FIG. 4 is a circuit diagram showing a filter unit of the image datacorrecting circuit according to the present embodiment.

FIG. 5 is a flowchart showing operations of the electronic still cameraaccording to the present embodiment.

FIG. 6 is a flowchart showing operations of the electronic still cameraaccording to the present embodiment.

FIG. 7 is a flowchart showing operations of the electronic still cameraaccording to the present embodiment.

FIG. 8 is a flowchart showing operations of the electronic still cameraaccording to the present embodiment.

FIG. 9 shows a display screen obtained at the time of recording asnapshot by the electronic still camera, according to the presentembodiment.

FIG. 10 is provided for describing a usage mode of a frame buffer,according to the present embodiment.

FIG. 11 is provided for describing another example of the usage mode ofthe frame buffer, according to the present embodiment.

THE BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block circuit diagram showing an electronic still camera 1utilizing JPEG and MPEG method according to an embodiment.

The electronic still camera 1 comprises an image pickup device 2, asignal processing circuit 3, an image data correcting circuit 4, a JPEGcore circuit 5, an MPEG core circuit 6, a frame buffer 7, a displaycircuit 8, a display 9, a memory card 10, input-output circuit 11, databuses 12 and 13, a control core circuit 14 and a group of operationalbuttons 15.

The control core circuit 14 controls each component 2-13 of theelectronic still camera 1 in response to an ON-OFF signal of the groupof operational buttons 15. The group of buttons 15 includes a stillpicture recording button 15 a, a moving picture recording button 15 band other selection buttons 15 c.

The image pickup device 2 comprises a CCD (Charge Coupled Device) and soforth, and shoots a subject image so as to generate an output signal.The signal processing circuit 3, which includes an A-D convertingcircuit, generates original image data, for example, whose pixel numberis vertical 1200× horizontal 1600, in units of picture, by performingwhite balance adjustment and gamma correction and so forth after theoutput signal of the image pickup device 2 is A-D converted. Theoriginal image data generated by the signal processing circuit 3 istransferred to either of the frame buffer 7 or the display circuit 8, orboth thereof via the data bus. The display circuit 8 generates an imagesignal from image data, in a single picture unit, transferred via thedata bus 12. The display 9 displays the image signal generated by thedisplay circuit 8, as a subject image.

The frame buffer 7 comprises a rewritable semiconductor memory such asSDRAM (Synchronous Dynamic RAM), DRAM, Rambus DRAM and the like, storespictures transferred via the data bus 12, namely, stores the image datain units of frame, and reads out the stored image data picture bypicture. In this frame buffer 7, there is provided a memory area 7 a(hereinafter referred to also as a memory area for use in pushing aside7 a) which temporarily pushes aside applicable still image data for oneframe and stores it in response to an ON signal of the still picturerecording button 15 a during recording of moving images.

The picture-by-picture image data read out from the frame buffer 7 aretransferred to the image data correction unit 4 via the data bus 12. Theimage data correction circuit 4 performs a correction processing, whichwill be described later, on image data inputted from the signalprocessing circuit 3. The picture-by-picture image data, generated fromthe image data correcting circuit 4, on which the correction processinghas been performed, are transferred to the JPEG core circuit 5 or theMPEG core circuit 6 via the data bus 12.

The memory card 10 is mounted on the electronic still camera 1 in adetachable manner and includes a flash memory 10 a therein. The flashmemory 10 a stores picture-by-picture compressed image data transferredvia the data bus 13, and reads out the stored compressed image datapicture by picture so as to be outputted to the data bus 13.

The input-output circuit 11 outputs picture-by-picture image datatransferred via the data bus 13 to external apparatuses connected to theelectronic still camera 1, for example, an external display, a personalcomputer, a printer or the like, and outputs image data inputted fromthese external apparatuses, to the data bus 13. The image data read outfrom the memory card 10 or the image data inputted via the input-outputcircuit 11 are transferred to the JPEG core circuit 5 or the MPEG corecircuit 6 via the data bus 13.

As shown in FIG. 2, the JPEG core circuit 5 comprises a DCT circuit 16,a quantization circuit 17, a Huffman coding circuit 18, a Huffmandecoding circuit 19, an inverse quantization circuit 20, and an inverseDCT (IDCT; Inverse DCT) circuit 21. In the JPEG core circuit 5, imagedata of one picture are divided into a plurality of macroblocks set bystandards of the JPEG method, and then a compression-expansionprocessing is performed thereon for each block. The DCT circuit 16, thequantization circuit 17 and the Huffman coding circuit 18 constitute aJPEG encoder so as to perform the compression-coding processing on stillimage data, and the Huffman decoding circuit 19, the inversequantization circuit 20 and the inverse DCT circuit 21 constitute a JPEGdecoder. The JPEG core circuit 5 or the JPEG encoder serves as anexample of “a still image encoder” in the present invention.

The DCT circuit 16 takes in image data of one picture in one block unit,against picture-by-picture image data read out from the frame buffer 7,and a two-dimensional discrete cosine transform (DCT: Discrete CosineTransform) is performed on the image data so as to generate DCTcoefficients. The quantization circuit 17 quantizes the DCT coefficientsupplied from the DCT circuit 16, by referring to a quantizationthreshold value stored in a quantization table stored in a RAM (notshown).

The Huffman coding circuit 18 performs variable-length coding on the DCTcoefficients quantized by the quantization circuit 17, by referring toHuffman codes stored in a Huffman table stored in a RAM (not shown), sothat compressed image data are generated picture by picture. Thecompressed image data generated by the Huffman coding circuit 18 aretransferred to at least one of the memory card 10 or the input-outputcircuit 11 via the data bus 13.

The MPEG core circuit 6 is constituted by adding first and second MC(motion compensated prediction) circuits 22 a and 22 b to the Huffmancoding circuit 18. Thus, the DCT circuit 16, quantization circuit 17,Huffman coding circuit 18, Huffman decoding circuit 19, inversequantization circuit 20, and inverse DCT circuit 21 are shared by theJPEG core circuit 5 and the MPEG core circuit 6, and whether to use theJPEG core circuit 5 or the MPEG core circuit 6 in which the first andsecond MC circuits 22 a and 22 b are added to this circuit 5 is selectedby a switch signal from the control core circuit 14. It is presupposedthat the JPEG and the MPEG are provided with the above-describedquantization table and Huffman table, separately.

In the MPEG core circuit 6, image data of one picture are divided into aplurality of macroblocks set by standards of the MPEG method, and then acompression-expansion processing is performed thereon for each block.The DCT circuit 16, the quantization circuit 17, the Huffman codingcircuit 18 and the first MC circuit 22 a constitute an MPEG encoder soas to perform the compression-coding processing on moving image data,and the Huffman decoding circuit 19, the inverse quantization circuit 20and the inverse DCT circuit 21 and the second MC circuit 22 b constitutean MPEG decoder. The MPEG core circuit 6 or the MPEG encoder serves asan example of “a moving image encoder” in the present invention. Thecompressed image data generated by the MPEG encoder, too, aretransferred to at least one of the memory card 10 or the input-outputcircuit 11 via the data bus 13.

In the JPEG core circuit 5 or the MPEG core circuit 6, the Huffmandecoding circuit 19 performs the variable-length decoding on thepicture-by-picture compressed image data transferred via the data bus 13by referring to Huffman codes, so that expanded image data are generatedpicture by picture. The inverse quantization circuit 20inverse-quantizes the picture-by-picture expanded image data generatedby the Huffman decoding circuit 19, by referring to the quantizationthreshold value, so as to generate DCT coefficients.

The inverse DCT circuit 21 performs the two-dimensional inverse discretecosine transform (IDCT: Inverse DCT) on the DCT coefficients generatedby the inverse quantization circuit 20. In the MPEG core circuit 6, thesecond MC circuit 22 b performs an MC processing on thepicture-by-picture expanded image data on which the inverse discretecosine transform has been performed by the inverse DCT circuit 21.

The expanded image data from the JPEG core circuit 5 or the MPEG corecircuit 6 are transferred to the frame buffer 7 via the data bus 12. Theframe buffer 7 stores the transferred picture-by-picture image data. Thedisplay circuit 8 generates an image signal, from the picture-by-pictureimage data transferred from the frame buffer 7 via the data bus 12, sothat the signal is displayed on the display 9 as a subject image.

As shown in FIG. 3, the image data correcting unit 4 comprises a digitalfilter unit 23, a ROM 24 and a timing control unit 25. The digitalfilter unit 23 includes a spatial filter which is a non-cyclic typedigital filter, for example, an FIR (Finite Impulse Response) filter.The digital filter unit 23 comprises, as shown in FIG. 4, n units ofdelay elements 26 . . . , which delay n bits of input signal inputtedfrom the signal processing circuit 3 for every sampling cycle, n+1 unitsof multipliers 27 . . . , and an adder 28 which convolutes signals fromthe multipliers 27 . . . . The respective coefficients a_(n), a_(n−1) .. . a₂, a₁ of the multipliers 27 . . . are coefficients that determinethe characteristics of the filter, and coefficients for use with afiltering processing of the moving image data and those for use with afiltering processing of the still image data are written in advance inthe ROM 24. These coefficients are in advance set to proper valuesthrough simulation at a manufacturing stage.

For example, when the moving image data are filtering-processed,satisfactory low-pixel-density images are achieved by changing the valueof each coefficient for every sampling cycle by the use of the conceptsof linear interpolation and others. As an example, let us consider thecase of reducing the horizontal number of pixels to ⅔. Suppose thatthere are three pixels p₁ to p₃ placed side by side horizontally in anoriginal image. Now these pixels are converted into two pixels q₁ and q₂by the filtering processing for the moving image data. To accomplishthis, q₁ and q₂ are each expressed as primary linear sum of p₁, p₂ andp₃. Namely, a filtering processing for reducing a data amount isrealized by determining each coefficient of the linear sums byexperiment or like means upon deciding on the ratio by which to expressa degree of reduction in the number of pixels. As an example, the numberof pixels may be reduced to 480 (vertical)×720 (horizontal).

On the other hand, when the filtering processing is performed on thestill image data, a high-pass filter may be formed by setting eachcoefficient so that a high-frequency region is emphasized. Thereby, asharp image having less deterioration at edge portions can be obtainedwhile the number of pixels is kept at a constant rate. Though n=8 is setin the present embodiment, this of course may vary according to thefreedom of designing.

The timing control unit 25 controls the timing at which the coefficientis read out from the ROM 24, the timing of the latch of input-outputdata, the timing of filter operation and so forth, according to thecontrol of the control core circuit 14.

Based on the above-described structure, operations for recording theimage data will be described with reference to flowcharts shown in FIG.5 to FIG. 8. In FIG. 5, the still image processing shown in FIG. 6 isperformed when the still picture recording button 15 a is switched ONwhile the moving image processing shown in FIG. 7 is performed when themoving picture recording button 15 b is switched ON.

(Still Image Recording)

Referring to FIG. 6, an original image signal taken in from the imagepickup device 2 is inputted to the signal processing circuit 3 at atiming corresponding to the ON signal of the still picture recordingbutton 15 a and is then converted to digital original image data of onepicture, so as to be taken into the frame buffer 7 (S1). The originalimage data of one picture are sent out from the frame buffer 7 to theimage data correcting circuit 4 and are also sent out to the displaycircuit 8, so that the still image is displayed on the display 9 (S2).

The above-described correction processing designed for handling thestill image is performed on the data taken in the image data correctingcircuit 4 (S3), and the corrected data are inputted to the JPEG corecircuit 5. Then, after a predetermined compression-coding processing isperformed thereon (S4), they will be recorded in the flash memory 10 a(S5).

(Moving Image Recording)

Referring to FIG. 7, the original image signal taken in from the imagepickup device 2 is inputted to the signal processing circuit 3 at atiming corresponding to the ON signal of the moving picture recordingbutton 15 b and is then converted to picture-by-picture digital originalimage data, so as to be successively taken into the frame buffer 7(S11). The picture-by-picture original image data are sent out from theframe buffer 7 to the image data correcting circuit 4 and are also sentout to the display circuit 8, so that the moving image is displayed onthe display 9 (S12).

The above-described correction processing designed for handling themoving image is performed on the data successively taken in the imagedata correcting circuit 4 (S13), and the corrected data are inputted tothe MPEG core circuit 6. Then, after a predetermined compression-codingprocessing is performed thereon (S14), they will be recorded in theflash memory 10 a (S15). This operation continues until the ON signal isagain sent out from the moving picture recording button 15 b (S16).

(Snapshot Recording)

Referring to FIG. 7, when the ON signal is sent out from the stillpicture recording button 15 a during the recording of the moving image,the control core circuit 14 judges that snapshot shooting is instructedfrom an external source and then executes a snapshot processing shown inFIG. 8 (S17). Then, image data for one frame are temporarily pushedaside and stored in the memory area 7 a for use in pushing aside in theframe buffer 7 (S21). During this pushing-aside operation, the recordingof the moving image continues. In other words, the original image signaltaken in from the image pickup device 2 is inputted to the signalprocessing circuit 3 and is then converted to picture-by-picture digitaloriginal image data, so as to be successively taken into the framebuffer 7 (S22). The picture-by-picture original image data are sent outfrom the frame buffer 7 to the image data correcting circuit 4 and arealso sent out to the display circuit 8. The above-described correctionprocessing designed for handling the moving image is performed on thedata successively taken in the image data correcting circuit 4 (S23),and the corrected data are inputted to the MPEG core circuit 6. Then,after a predetermined compression-coding processing is performed thereon(S24), they will be recorded in the flash memory 10 a (S25).

In the present embodiment, the picture-by-picture original image dataare sent out from the frame buffer 7 to the display circuit and,together with this, the image data for one frame pushed aside in thememory area for use in pushing aside 7 a are sent out. The moving imageof being presently shot and the still image to be recorded as a snapshotare displayed in parallel (S26) on the display 9. FIG. 9 shows anexample of the moving image and the still image being displayed on thedisplay 9 in parallel, where a moving image 200 whose size is 1/16 ofthe picture is displayed in the upper right position of a screen while astill image 100 is displayed as a main picture.

The still image is displayed for predetermined time duration, forexample, for five seconds and, thereafter, the display is switched todisplay of the moving image alone (S27) and the operation is returned tothe normal display image processing shown in FIG. 7 (S28). During theparallel display of the still image the user can confirm on the display9 whether or not a desired snapshot was shot. When the ON signal isagain sent out from the still picture recording button 15 a during thedisplay of the still image, the processings of S21 to S27 are performedbased on the data taken in at a timing corresponding to the ON signal(S29). In this case, the contents of the memory area for use in pushingaside 7 a are replaced by new data.

FIG. 10 is provided for explaining a usage state of the frame buffer 7in the moving image processing and snapshot processing. The frame buffer7 is provided with four normal memory areas A to D, and one picture,that is data for one frame, is stored for each memory area A-D. Ofcourse, the number of the memory areas is changed as appropriateaccording to specifications of the camera 1.

In the normal moving image processing shown in FIG. 7, as shown in FIG.10( a), the picture-by-picture digital original data from the signalprocessing circuit 3 are stored in the order of A→B→C→D and areoutputted to the data bus 12 in the order starting from the one inputtedfirst (First-In First-Out). When the data are stored in the last memoryarea D, the memory area A is again used. Namely, the memory areas A to Dare used cyclically. For the cyclic use of the frame buffer 7, an LRU(Least Recently Used) algorithm and others such as a page memory controlmethod may be adopted.

When the ON signal for a snapshot is sent out from the still picturerecording button 15 a during the processing of the moving images, thedata taken in at a timing corresponding to the ON signal is stored in acertain memory area and said area is used, as it is, as the memory area7 a for use in pushing aside the still image data. For example, whendata taken in at a timing of recording a snapshot are stored in thethird memory area C, the memory area C is used as the memory area 7 afor use in pushing aside, as shown in FIG. 10( b), and in the movingimage processing thereafter the remaining memory areas A, B and D areused cyclically. Thereafter, when another data taken in again at atiming of recording a snapshot are stored in the second memory area Bthis time, the data at the third memory area C are cancelled, that is,the data are removed from a protected subject and the second memory areaB is used as the memory area for use in pushing aside 7 a, as shown inFIG. 10( c), and in the moving image processing thereafter the memoryareas A, C and D other than the second memory area B are usedcyclically.

As described above, the order in which the four memory areas A to D areused depends on the algorithm to be implemented; the memory areas may beused in the order, for example, ACDBAC . . . or ACDABC . . . or thelike. In short, when there exist a plurality of memory areas which havestored processing-completed moving image data, that are, the movingimage data in which overwriting thereof is allowed, any memory area maybe utilized for use in pushing aside the data. In these cases too, suchusage is called “cyclically used.” When only two of the memory areas areprepared at first, the recording data of a snapshot are stored, so thatthe moving image data thereafter are successively outputted after themoving image data are taken in to a single memory area. In this casetoo, it is called “cyclically used.”

When the moving image recording is completed, the control core circuit14 judges whether or not the pushing-aside operation of the still imageis performed during the recording of the moving image (S18) as shown inFIG. 7; if performed, the data, for one frame, which are being stored inthe memory area for use in pushing aside 7 a are transferred to theimage data correcting circuit 4 via the data bus 12 and the similarprocessing to the still image recording is performed (S19).

The electronic still camera 1 according to the present embodimentprovides the following operation and effects.

(1) Since the still image can be extracted as a snapshot during shootingof the moving image, the function as an electronic still cameraimproves.

(2) Since the still image is displayed as a snapshot on the display 9,the user can easily confirm a shooting state of the snapshot and he/shecan take another snapshot in no time if he/she doesn't like thesnapshot. Thereby, frequency of mis-shooting snapshots can be reduced.Thus, the value of merchandise as an electronic still camera can beraised.

(3) In addition to the above (2), the moving image which is presentlybeing shot is displayed in parallel, so that a shooting state of themoving image can also be confirmed in real time.

(4) In addition to above (2) and (3), a shooting state of the snapshotcan be easily confirmed by displaying the still image to be recorded asa main picture on the display 9 while the moving image is displayed in asmall size.

(5) In addition to the above (2), since the still image to be recordedas a snapshot is displayed temporarily on the display 9, the operationnecessary for confirming the recording of the moving images on thedisplay 9 will not be interfered for long period of time.

(6) As shown in FIG. 10, the memory area for use in pushing aside 7 awill not be provided until a still shooting for a snapshot is instructedand all are utilized as normal memory areas, so that use efficiency ofthe frame buffer 7 is enhanced.

(7) The still image data can be corrected to a further optimal image byusing the data correcting circuit 4.

(8) Since it is so structured that not only the moving image data butalso the still image data passes through the data correcting circuit 4,the still image can also be correction-processed by merely storingcoefficients in the ROM 24, thus realizing low cost and functionimprovement. Since no correcting circuiting for exclusive use with thestill image needs to be provided, the tendency of the apparatus tobecome large-sized as well as the increase in power consumed can beprevented.

(9) The DCT circuit 16, the quantization circuit 17, the Huffman codingcircuit 18, the Huffman decoding circuit 19, the inverse quantizationcircuit 20 and the inverse DCT (IDCT; Inverse DCT) circuit 21 are sharedin the JPEG core circuit 5 and the MPEG core circuit 6, so that thestructure of the electronic still camera 1, an arithmetic processingalgorithm and so forth can be simplified.

(10) Provision of the memory area 7 a for use in pushing aside for thesnapshot facilitates the sorting and search of the still image and themoving image, and makes possible a faster reproduction.

(11) When the snapshot shooting is instructed, image data prior to beinginputted to the image data correcting circuit 4 are pushed aside; as aresult, filtering processing and zooming processing in the verticaldirection will be facilitated when thereafter processing the data at theimage data correcting circuit 4, and the moving images can be recordedwithout being interrupted.

The present embodiments include the following modified examples.

(i) At S26 in FIG. 8, the still image alone is displayed on the display9.

(ii) At S26 in FIG. 8, the size of the still image and that of themoving image displayed on the display 9 in parallel are reversed, sothat the moving image becomes the main picture. Moreover, a structure isprovided such that permission and denial of the display of the stillimage can be instructed by the user using a button or the like.

(iii) At S29 in FIG. 8, image data for a newly taken snapshot is storedin parallel with old data which is not replaced thereby. Namely, asshown in FIG. 11, in the normal moving image processing the memory areasA-D of the frame buffer 7 are used cyclically (FIG. 11( a)). Next, whendata taken in at a timing the first snapshot is recorded is stored inthe third memory area C, the memory area C is used as the memory areafor use in pushing aside 7 a (FIG. 11( b)), and in the moving imageprocessing thereafter, the remaining three memory areas A, B and D areused cyclically. When data taken in at a timing the second snapshot isrecorded is stored in the second memory area B, the second and thirdmemory areas B and C are used as the memory area for use with pushingaside 7 a (FIG. 11( c)), and in the moving image processing thereafter,two memory areas A and D are used cyclically, that is, alternately. Inthis manner, a plurality of snapshots can be recorded. Increasing thenumber of snapshots, which can be taken, will reduce the area in whichthe frame buffer 7 can be used in the moving image processing. Thus, thenumber of snapshots which can be taken needs to be set to the degreethat overflow of the frame buffer 7 does not occur at the time ofprocessing the moving images.

(iv) A magneto-optical disk, optical disk, magnetic disk or the like isused in place of the memory card 10.

(v) When the shooting for taking a snapshot is instructed, the imagedata in which a processing has been completed at the image datacorrecting circuit 4 are temporarily pushed aside to the memory area foruse in pushing aside 7 a. By so doing, the data can be easily taken outwhen a predetermined compression processing is performed in the JPEGcore circuit 5 thereafter.

(vi) The still image data do not go through the image data correctingcircuit 4.

(vii) The M-JPEG techniques are used in compression and expansion of themoving image data.

(viii) In addition to JPEG used for the compression and expansion of thestill image data, compression technology using thedifference-processing-based difference YUV, the block-based Hadamardtransform, the Slant transform or Haar transform method is used for thecompression of the still image data.

(ix) When the filtering processing is performed on the still image data,a low-pass filter, a band-pass filter or the like may be formed bysetting each coefficient value so that a high frequency range is notemphasized. Thereby, the aliasing or jaggy may be suppressed.

(x) When the filtering processing is performed on the still image data,a dynamic range of a color signal is extended and each coefficient valueis set so as to obtain a vivid image. Besides, arbitrary linear ornonlinear filter can be used in accordance with use or user's taste.

(xi) As shown in FIG. 1, the selection button 15 c is provided whichselects the correcting functions of the above embodiments and the above(ix) and (x). Thereby, the still image in accordance with the user'staste can be formed, and the function as the electronic still camera 1is further enhanced. The selection button 15 c is an example of a“selector” in the present invention.

(xii) The filtering processing in the image data correcting circuit 4may be such that the filtering processing can be set to the identitytransform processing. In that case, the still image data inputted areoutputted as kept intact. In this structure, the filter function can beeasily put to effective use when necessary. In order to realize theidentity transform, for example, in FIG. 4, coefficient α₁ only is setto 1 and the remaining coefficients α_(n−1) . . . α₂, α₁ are all set to0. The present invention is characterized in the feature that the stillimage data and the moving image data are made to pass through the imagedata correcting circuit 4, and the identity transform processing, ofcourse, belongs to the concept of the filtering processing.

(xiii) Though described is that either the snapshot or the moving imageis displayed in the main picture, which one is to be set to the mainpicture may be user-selectable. The control core circuit 14 may switchwhich one is set to the main picture, by the operation of the selectionbutton 15 c or the like by the user. Moreover, the control core circuit14 may include a mode by which the display of the snapshot is prohibitedaccording to the user's instruction, or the snapshot may be displayedfor the time duration specified by the user.

INDUSTRIAL USABILITY

As have been described, the present invention can be used for thedigital camera or the image processing method, image processingapparatus and the memory control circuit which can be used therefor.

1. a digital camera comprising: a storage unit which includes a memoryarea to sequentially and temporarily store moving image data comprisinga series of frames; a display control unit which generates an imagesignal from the series of frames in the memory area to display a seriesof images as a moving image on a display; and a control unit whichresponsive to a still image capture instruction signal to be input whenthe series of images is being displayed as the moving image, on thedisplay as a moving image, assigns part of captures a single framestored in the memory area, the single frame corresponding to one of theseries of images on the display when the still image capture instructionsignal is input, so as to maintain the captured single frame in thememory area to, instructs said display control unit to display on thedisplay a still image from the captured single frame stored in thememory assigned area together with the moving image and instructs saiddisplay control unit to stop display on the display the still imagetogether with the moving image if still image capture instruction signalis not inputted after a predetermined time, wherein when the singleframe is captured, the storage unit sequentially and temporarilyoverwrites previous moving image data with subsequent moving image datain the memory area other than an area where the captured single frame ismaintained.
 2. A digital camera as recited in claim 1, furthercomprising a unit which inputs the still image capture instructionsignal.
 3. A digital camera as recited in claim 1, wherein said controlunit controls said display control unit in a manner such that a stillimage displayed during display of a moving image is displayed on thedisplay in parallel with the moving image.
 4. A digital camera asrecited in claim 3, wherein said control unit controls said displaycontrol unit in a manner such that the still image is set to a mainpicture of the display so as to be displayed thereon.
 5. A digitalcamera as recited in claim 3, wherein said control unit controls saiddisplay control unit in a manner such that the moving image is set to amain picture of the display so as to be displayed thereon.
 6. A digitalcamera as recited in claim 1, wherein said control unit controls saiddisplay control unit in a manner such that the still image is displayedfor a predetermined period of time.
 7. A digital camera as recited inclaim 1, wherein said control unit controls said display control unit ina manner such that either the still image or the moving image isselected in a switchable manner and thus is set to a main picture of thedisplay so as to be displayed thereon.
 8. A digital camera as recited inclaim 1, wherein said control unit sets said display control unit in amanner that permission/denial of display of the still image isswitchable.
 9. A digital camera as recited in claim 1, wherein saidcontrol unit controls said display control unit in a manner that thestill image is displayed for time duration only according to a user'sinstruction.
 10. A digital camera, comprising: a storage unit whichincludes a memory area to sequentially and temporarily store movingimage data comprising a series of frames; a moving image encoder whichcodes the shot image data read from the storage unit as a moving imagecomprising a plurality of frames; a display control unit which generatesan image signal from the series of frames in the memory area to displaya series of images as a moving image on a display; a control unit which,responsive to a still image capture instruction signal to be input whenthe series of images is being displayed as the moving image, captures asingle frame stored in the memory area, the single frame correspondingto one of the series of images on the display when the still imagecapture instruction signal is input, so as to maintain the capturedsingle frame in the memory area, instructs said display control unit todisplay on the display a still image from the captured single framestored in the memory area together with the moving image and instructssaid display control unit to stop display on the display the still imagetogether with the moving image if still image capture instruction signalis not inputted after a predetermined time; the storage unitsequentially and temporarily overwriting previous moving image data withsubsequent moving image data in the memory area other than an area wherethe captured single frame is maintained when the single frame iscaptured; a still image encoder which codes the captured single framefrom the storage unit; a moving image encoder which codes the movingimage data read from the storage unit; and an interface for an externalmemory which records the captured single frame coded by said still imageencoder and the moving image data coded by said moving image encoder.11. A digital camera as recited in claim 10, further comprising a unitwhich inputs the still image capture instruction signal.
 12. A digitalcamera as recited in claim 10, wherein said control unit controls saiddisplay control unit in a manner such that a still image displayedduring display of a moving image is displayed on the display in parallelwith the moving image.
 13. A digital camera as recited in claim 12,wherein said control unit controls said display control unit in a mannersuch that the still image is set to a main picture of the display so asto be displayed thereon.
 14. A digital camera as recited in claim 12,wherein said control unit controls said display control unit in a mannersuch that the moving image is set to a main picture of the display so asto be displayed thereon.
 15. A digital camera as recited in claim 10,wherein said control unit controls said display control unit in a mannersuch that the still image is displayed for a predetermined period oftime.
 16. A digital camera as recited in claim 10, wherein a coding unitof said still image encoder and that of said moving image encoder areshared in common.
 17. A digital camera as recited in claim 10, whereinsaid control unit controls said display control unit in a manner suchthat either the still image or the moving image is selected in aswitchable manner and thus is set to a main picture of the display so asto be displayed thereon.
 18. A digital camera as recited in claim 10,wherein said control unit sets said display control unit in a mannerthat permission/denial of display of the still image is switchable. 19.A digital camera as recited in claim 10, wherein said control unitcontrols said display control unit in a manner that the still image isdisplayed for time duration only according to a user's instruction.